1. Field of the Invention
This invention relates to making black glass by utilizing waste glass recovered from the residue of municipal trash burning incinerators and the like. The invention produces black glass that possesses properties of heat absorption and transmissivity of solar rays.
Incineration is a primary form of solid waste disposal, especially in large cities, whereby trash is burned under temperatures ranging from 1400.degree. F. to 2000.degree. F. Upon completion of incineration of the trash, a residue remains that is comprised for the most part of unburnable objects. Depending on weather patterns, efficiency of the incinerator, and trash collection standards, the residue may also contain burnable, but only partially burned objects, such as carpets, phone books, and organic matter.
Analysis of the content of typical municipal incinerator residue, as conducted by the U.S. Bureau of Mines, shows the following composition on a dry basis and assuming a complete burnout:
______________________________________ wire and large iron 3.0% tin cans 13.6% small ferrous metals 13.9% non-ferrous metal 2.8% glass 49.6% ash 17.1% ______________________________________
(See Bureau of Mines Information Circular 8533, Cost Evaluation of a Metal and Mineral Recovery Process for Treating Municipal Incinerator Residues, 1971, pp. 2-3).
While raw trash content may vary from area to area, and city to city, incinerator residue is generally consistent. (See Bureau of Mines Circular 8533, p. 2) Only the proportions of the contents may vary slightly from community to community.
This residue has always been a disposal problem, and cities typically landfill the residue. There exists a number of practices for separating the ferrous metals from the residue for recycling. The U.S. Bureau of Mines and the U.S. Department of Transportation have also sponsored research into uses of incinerator residue for making glass wool, bricks, blocks, and also as an aggregate in highway construction materials. (See U.S. Bureau of Mines Information Circular 8533, an Federal Highway Administration Report No. FWWA-RD-79-83, Evaluation of the Economic and Environmental Feasibility of Using Fused and Unfused Incinerator Residue in Highway Construction, April, 1979).
2. Prior Art
U.S. Pat. No. 3,907,582 uses residue from a refuse incinerator for an asphaltic road composition. Also, some incinerator residue is used directly as a sub-base course and soil stabilization resource. Yet, there is still only a very small amount of recycling of the incinerator residue, with most residue still being landfilled.
Previous research and applications have involved separation, sorting, and processing of incinerator residue components for use in other materials (e.g., glass wool, bricks, asphalt, etc.) There has been no previously known application that transforms the waste glass component into a black glass material that is especially suitable for use in the field of solar energy.
The prior art has established the use of waste materials in the production of ceramic and glass bodies. U.S. Pat. No. 2,576,565 relates to the use of waste fly ash material from coal burning plants for making ceramic products such as bricks, tiles, or pipes. Russian Pat. Nos. 289,064 of 1970 and 415,242 of 1974 teach the use of ash and slag recovered from steel making and power station furnaces, with additives, to produce black colored glass useful as building materials. Great Britain Pat. Nos. 5,671 of 1906 and 244,358 of 1925 cover the use of refuse ashes and town refuse components for the manufacture of blocks and other building glassware.
None of the known prior art teaches the use of municipal incinerator residue waste glass to produce black glass. U.S. Pat. No. 2,576,565 burns out carbon to cause a red coloration for ceramics made from waste fly ash. The Russian Patents use additives to slag and fly ash from power stations to create black glass. The British Patents use incinerator residue glass finely ground as a binder in making glass and building blocks. The British Patents do not result in black glass; the Russian Patents do not use waste glass from incinerated trash; and U.S. Pat. No. 2,576,565 results in a red product.